Hi Jeroen,
Thanks for writing back.
On Mon, Jun 29, 2015 at 18:50:47 +0200, Jeroen Massar wrote:
Recently, it looks like my home Cablecom connection was migrated to a DS-Lite setup.
[...] What contract do you have btw, is it the 'free' edition or are you actually paying a hefty amount of money for this kind of 'service'?
It's a quite expensive package (95.-/month)...
dws@shuttle:~$ ping -s 1433 8.8.8.8 PING 8.8.8.8 (8.8.8.8) 1433(1461) bytes of data. From 192.0.0.2 icmp_seq=1 Frag needed and DF set (mtu = 1474) From 192.0.0.2 icmp_seq=2 Frag needed and DF set (mtu = 1474) From 192.0.0.2 icmp_seq=3 Frag needed and DF set (mtu = 1474)
192.0.0.2 is in the DS-LITE /24. Thus that is a node of theirs reporting this.
But there is not directly anything wrong with the above, just means that your box needs to fragment it and they don't do it for you (as that would mean state and then the thing will really completely burn down).
Are you sure that there isn't anything wrong with the above? It seems to me that Path MTU discovery can't work, if the MTU reported by the router is not correct. That there is no other ICMP message from any other router.
So some Cablecom router is sending ICMP errors saying that I should fragment the packets to at most 1474 bytes, when in fact I am sending packets that are 1461 bytes long.
Likely that is missing the overhead of the tunneled traffic.
Yes, I guess so too.
Cheers David